Synthesis of (±)-thaps-7(15)-ene and (±)-thaps-6-enes
作者： Adusumilli Srikrishna , Kathiresan Krishnan
DOI: 10.1039/P19930000667
关键词: Organic chemistry 、 Ketone 、 Orthoester 、 Diazo 、 Enone 、 Chemistry 、 Wittig reaction 、 Ene reaction 、 Claisen rearrangement 、 Cyclopropanation
摘要: The synthesis of (±)-3a,4,4,7a-tetramethylhydrindan-2-one 8, containing three contiguous quaternary carbons as present in thapsanes, and the total thaps-7(15)-ene 6 thaps-6-ene 7, probable biogenetic precursors have been achieved. Thus, orthoester Claisen rearrangement cyclogeraniol 14, followed by hydrolysis resultant ester 16 furnished eneacid 13. Copper sulfate-catalysed intramolecular cyclopropanation diazo ketone 18, derived from acid 13, generated cyclopropyl 12. Regiospecific reductive cleavage 12 hydrindanone whereas 26 28avia 27. Wittig methylenation 28a 6, which on isomerisation gave 7. Allylic oxidation thapsenone 31, a degradation product natural thapsane 1b.
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